[0001] Printers are widely used with computing equipment for obtaining hard copies of documents/data shown on the display screens of the computing equipment. MFPs (Multi-Function Printers) are now used in homes and offices and also in bigger business settings as part of larger document management systems. Functionalities such as copying, scanning, emailing and faxing are now available in the MFPs in addition to more sophisticated printing modes such as duplex printing. A page-wide array of nozzles in a printer produces ink drops which are delivered onto a paper via precise control of paper motion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Features of the present disclosure are illustrated by way of example and not limited in the following figure(s), in which like numerals indicate like elements, and in which:

[0003] Figure 1 shows a schematic diagram of an example media drive mechanism for a printer.

[0004] Figure 2 illustrates the motion of a media in accordance with a bidirectional scheme of motion of the first and second rollers depicted in Figure 1 .

[0005] Figure 3 illustrates the motion of a media in accordance with a unidirectional scheme of motion for the first and second rollers depicted in Figure 1 .

[0006] Figure 4 illustrates a motion of a media in a multiple-zone unidirectional scheme of motion in accordance with an example of the present disclosure.

[0007] Figure 5 is a schematic diagram that shows the media being driven by a motion scheme in which a pair of additional edge sensors are used for determining the position of the media in accordance with an example of the present disclosure.

[0008] Figure 6 illustrates a flowchart of an example method of inducing a skew to move a media along the media feed direction.

[0009] Figure 7 is a flowchart of an example method of activating rollers in accordance with a bi-directional single-zone scheme.

[0010] Figure 8 is a flowchart of an example method of activating rollers in accordance with a scheme wherein an induced skew is corrected to shift the media perpendicular to the media feed direction. DETAILED DESCRIPTION

[0011] For simplicity and illustrative purposes, the present disclosure is described by referring mainly to an example thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be readily apparent however, that the present disclosure may be practiced without limitation to these specific details. In other instances, some methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure. In the present disclosure, the term "includes" means includes but not limited thereto, the term "including" means including but not limited thereto. The term "based on" means based at least in part on. In addition, the terms "a" and "an" are intended to denote at least one of a particular element.

[0012] Printers generally move paper or media parallel to the paper axis or the media feed direction and perpendicular to the roller axes. By the way of illustration and not limitation, printing is achieved via a page-wide array of thousands of nozzles. Examples of printers are disclosed herein which comprise media moving mechanisms that 'induce' skew in the media repeatedly thereby shifting its center normal to the paper axis or media feed direction and parallel to the roller axis. A scanner array can be used to detect the shift in the edge of the media. The motion of the media progresses based on the detected shift and the desired skew. This enables certain technical effects such as but not limited to print head calibration, full bleed printing and front to back image registration on a duplex print job.

[0013] Currently re-used mass produced A sized (approximately 8.5 ^χ 1 1 inches) or A4 sized (approximately 8.27 ^x 1 1 .69 inches) scan bar or the scanner array is indexed perpendicular to the media feed direction to scan up to A3 sized (approximately 1 1 .69 x 16.53 inches) paper or media which is the limit of the indexing motion. The printhead is wider than the A3 sized media, placing the outermost nozzles in a 'blind zone' of the scanner array. The scanner array is made up of individual scanning heads/dies which have blind spots around the seams between the individual heads/dies. Hence, the outermost nozzles remain uncalibrated. In some printers, the scanner array is re-indexed until it is at an acceptable location. Inducing skew as detailed herein can move the image with sufficient accuracy so that the printed image is moved out of the blind zone thereby enabling calibration of even the outermost nozzles.

[0014] Another area that the methodologies for inducing skew described below improve is the full bleed printing wherein the image is printed until the edge of the media without any margins. A pagewide array printer capable of full bleed printing has a printhead that is wider than the widest media in order to allow full bleed printing due to inherent media to printhead registration errors. This also leads to higher cost due to the need for the printhead to be wider than the media. The methods for inducing skew which are discussed below, facilitate accurate media to printhead registration allowing the printhead to be just as wide as the widest media and yet be able to print full bleed. The methodologies also aid in registering front and back side images on a duplex print job. This is a very useful feature for printing on pre-printed forms that are well registered so that the printed images are accurately aligned with the corresponding cells.

[0015] Figure 1 shows a schematic diagram of a media drive mechanism 100 for a printer in accordance with an example. The media driving mechanism 100 comprises a processor 102, a memory 104 communicatively coupled to the processor 102 and having stored thereon instructions executed by the processor 102 to activate and control a drive mechanism 106 including a shaft (not shown) that drives a pair of rollers - a first roller 1 12 and a second roller 1 14. The memory 104 may be any suitable medium that participates in providing instructions to the processor 102 for execution. For example, the memory 104 may be non-volatile media, such as an optical or a magnetic disk; volatile media, such as memory. [0016] The rollers 1 12, 1 14 are positioned so that the second roller 1 14 is positioned at a distance from the first roller 1 12 perpendicular to the media feed direction. In an example, the first and second rollers 1 12, 1 14 can be referred to as the front and rear rollers respectively. Although one pair of rollers is shown in Figure 1 for brevity, however, many roller pairs (not shown) can be employed to induce the desired skew. In addition, the media drive mechanism 100 can include a scanner array 120 and optionally one or more edge sensors 122, 124 that enable determination of the skew induced in a media.

[0017] A media 1 16 to be printed on is moved by the first and second rollers 1 12, 1 14 under the control of the processor 102 which executes the instructions from the memory 104. In one example, the rollers 1 12, 1 14 are manipulated so that the media 1 16 is moved perpendicular to the paper axis X or perpendicular to the direction in which the media 1 16 is fed to the rollers 1 12, 1 14. Such motion is achieved by 'inducing' a skew in the position of the media 1 16 repeatedly via the rollers 1 12, 1 14. Attributes of the roller motion such as but not limited to, the degree of skew to induce, a scheme of motion to implement in order to achieve a desired skew and the number of iterations to execute can be determined by the processor 102 based on various factors. Some factors that the processor 102 employs to determine the motion attributes can include the position of the media 1 16, the distance by which the media 1 16 should be translated and a direction of such translation.

[0018] In an example, the direction and the distance of translation for the media 1 16 is also determined by the processor 102 based for example, on the technical effects that are to be achieved via such motion. Various technical effects can be achieved through the perpendicular motion as will be detailed further herein. Calibration of the print head, full bleed printing and front and back image registration are a few non-limiting examples of the technical effects that are improved via implementation of the methodologies discussed herein. The distance and the direction for the translation are determined by the processor 102 by executing the instructions 1062 from the memory 104. The direction and distance for the translation of the media 1 16 is used to determine the skew to induce in the media position relative to the media feed direction. The desired skew to induce can be determined by the processor 102 via executing the instructions 1064. In one example, simple geometric techniques can be used to determine the desired skew for inducing based on the translation of the media 1 16.

[0019] The desired skew to induce is further employed to select a scheme of motion for the rollers 1 12, 1 14 and to calculate the respective speeds for the rollers 1 12, 1 14. The processor 102 executes the instructions 1066 for selecting the scheme and calculating the speed differentials of the rollers 1 12, 1 14 for the selected scheme. Various uni-directional and bi-directional schemes can be implemented for the roller motions, such as but not limited to, 'a parallel park inversion' and 'skew correct to shift' or other schemes as detailed herein. The schemes determine the order in which the roller speeds are to be manipulated in order to achieve a desired final effect. Upon selection of the roller speeds and the scheme for their manipulation, the processor 102 sends signals to a shaft controlling the rollers via execution of the instructions 1068 to activate or rotate the rollers for the respective speeds in accordance with the selected scheme. Some schemes may be unidirectional wherein the media 1 16 is skewed while being fed in one direction whereas in other bi-directional schemes the media 1 16 maybe skewed while being fed in both, forward and backwards, directions in order to achieve its translation across a predetermined distance. In addition, multi-zone drive mechanisms may also be implemented wherein a plurality of the roller pairs are employed to achieve the translation of the media 1 16 across a predetermined distance. Execution of the instructions 1068 therefore, causes the first roller 1 12 and the second roller 1 14 to be rotated at the respective speeds in accordance with the selected scheme such that the desired skew is induced in the position of the media relative to the media feed direction.

[0020] Figure 2 illustrates the motion of a media in accordance with a selected bi-directional scheme of motion of the first and second rollers 1 12, 1 14. This scheme can be considered to be a conceptual inversion of a car parallel parking in which the car (rollers) is fixed in space and the road (media) can move around. At step I of the first selected scheme, the media 1 16 is loaded and an edge of the media 1 16 is scanned with the scanner array 120. Based on the scanner array information regarding initial loaded position of the media 1 16 at step I, the processor 102 can determine the direction and distance of translation of the media. Upon the determination of the direction and distance of translation of the media 1 16, the processor 102 can further determine the skew to induce and the speeds of rotation of the first and second rollers 1 12, 1 14. In accordance with the bi-directional, single zone scheme of rotation, the first roller 1 12 is initially rotated faster than the second roller 1 14 for a predetermined distance to advance the media 1 16 along the media feed direction at step II. At step III, the second roller 1 14 is rotated faster than the first roller for a predetermined distance to advance the media along the media feed direction. At step IV, the first roller 1 12 is again driven faster than the second roller 1 14 for a predetermined distance so that the media 1 16 recedes along the media feed direction. At step V, the second roller 1 14 is rotated faster than the first roller for a predetermined distance to cause the media 1 16 to recede along the media feed direction. At step VI, the media 1 16 is straight but shifted with respect to its initial position at step I. The media edge is again scanned at step VI to determine if the distance translated is sufficient or if further iterations of steps ll-V are required to move the media 1 16 further perpendicular to the media feed direction.

[0021] Figure 3 illustrates the motion of a media in accordance with a single zone, uni-directional scheme of motion for the first and second rollers 1 12, 1 14. At step I, the media 1 16 is loaded and an edge of the media 1 16 is scanned by a scanner array 120 to determine a direction and distance for the translation of the media 1 16. The respective speeds of rotation for the first and the second rollers are also determined by the processor 102. At step I I, the first roller 1 12 is rotated faster than the second roller 1 14 for a predetermined distance to advance the media 1 16 along the media feed direction. At step I I I, the second roller 1 14 is rotated faster than the first roller 1 12 to advance the media 1 16 along the media feed direction. As seen from Figure 3, the media 1 16 is straightened at step I I I and moved perpendicular to the media feed direction by a certain distance. If it is desired to move the media 1 16 further along the media feed direction, steps II and

111 may be repeated.

[0022] The schemes of motion discussed heretofore show a single pair of the first and second rollers 1 12, 1 14. In one example, multiple-zone drive mechanisms can be employed wherein multiple, independently driven roller pairs which are used for causing translation of the media 1 16 by a predetermined direction by a predetermined distance. Figure 4 illustrates a motion of a media 1 16 in a multiple-zone unidirectional scheme of motion. At step I, the direction and distance for translation is determined so that the speeds of the rollers 1 12, 1 14, 302, 304 and the number of iterations for which the motion scheme is to be repeated can be determined. In an example, the first pair of rollers 1 12, 1 14 and the second pair of rollers 302 and 304 are separated by a distance less than the media length along the media feed axis X. For such configuration, the first rollers

1 12 and 304 will rotate faster than the second rollers 302 and 1 14 for a predetermined distance to advance the media along the media feed axis at step I I . At step I I I, the second rollers 1 14, 302 will rotate faster than the first rollers 1 12, 304 for a predetermined distance to advance the media along the media feed direction. [0023] In an example, the first pair of rollers 1 12, 1 14 and the second pair of rollers 302 and 304 are separated by a distance greater than the media length along the media feed axis X. For such configuration, the first roller 304 of a second pair of rollers will rotate faster than the second roller 302 of the same pair for a predetermined distance to advance the media along the media feed direction. This motion of the rollers 302, 304 pushes the media 1 16 to the first pair of rollers 1 12, 1 14. At step III the second roller 1 14 of the first pair of rollers will be rotated faster than the first roller 1 12 of the first pair for a predetermined distance to advance the media along the media feed direction.

[0024] Figure 5 is a schematic diagram that shows the media 1 16 being driven by another motion scheme in which a pair of additional edge sensors 122, 124 may optionally be used for determining the position of the media 1 16 thereby configuring the media drive mechanism as a closed loop system. In an example, the scanner array 120 may be employed for determining the position of the media 1 16 as described above with respect to other schemes of motion thereby configuring the media drive mechanism as an open loop system thus avoiding the cost of addition sensor hardware.

[0025] At step I, the media is loaded and the edge is scanned with the scanner array 120. The direction and distance for moving the media 1 16 based on which the speeds of rotation of the rollers 1 12, 1 14 and the number of iterations for repeating the scheme is also determined. At step II, the first roller is rotated faster than the second roller thereby inducing skew to advance the media along the media feed direction. At step III, the media 1 16 is reversed through the duplex path even as the media is still positioned at an angle to the media feed direction. At step IV the skew may be measured, for example, by using the sensors 122, 124 and the measured skew is corrected via the motion of the first and the second rollers 1 12, 1 14. At step V, the skew correction process is concluded and the media is straightened and shifted along the media feed axis. At step V, the edge of the media 1 16 is scanned by the scanner array 120 and the aforementioned steps are repeated if needed to move the media 1 16 further along the media feed direction.

[0026] Figure 6 illustrates a flowchart 600 that details one example of a method of inducing a skew to move a media along the media feed direction. The method begins at 602, wherein an initial position of a media is detected. In an example, the distance and direction of traversal of the media along the media feed direction can determine the desired skew to induce in the initial or starting position of the media with respect to a media feed axis. Accordingly, the distance and direction of translation of the media 1 16 is determined at 604. At 606, a scheme of the motion for the rollers and the corresponding roller speeds are selected. In one example, the scheme can be selected from a plurality of schemes described herein subject to the availability of the requisite hardware. The rollers are activated at 608 to rotate at respective speeds in accordance with the selected scheme of motion. At 610, it is determined if the desired skew was induced. Such determination can be made, for example, via the position determination of the media by the sensor 122, 124 and the scanner array. If it is determined at 610 that the desired skew is induced, the rotatory motion of the rollers is ceased and the process terminates on the end block. If it is determined at 610 that the desired skew is not yet achieved, the process returns to 608 to further activate the rollers.

[0027] Figure 7 is a flowchart 700 that details a method of activating the rollers in accordance with a bi-directional, single-zone scheme. In accordance with this scheme, the first roller is driven or rotated faster than the second roller as shown at 702. In an example, the first roller is a front roller and the second roller is a rear roller and the rollers are spaced apart such that the second roller is positioned at a location with respect to the first roller that is perpendicular to the media feed direction. At 704, the second roller is rotated faster than the first roller for a predetermined distance along the media feed axis. At 706, the first roller is rotated faster than the second roller for a predetermined distance so that the media recedes or reverses along the media feed axis. At 708, the second roller is rotated faster than the first roller for a predetermined distance so that the media recedes along the media feed axis. For a uni-directional, single-zone scheme the rollers are activated so that the media 1 16 is skewed while it moves in one direction along the media feed axis. In an example, that includes multiple zones, the second roller of a pair of rollers may be initially rotated faster than the first roller of that pair and subsequently, the first roller of another pair of rollers are rotated faster than the second roller of the other pair.

[0028] Figure 8 is a flowchart 800 that details a method of activating the rollers in accordance with a scheme wherein an induced skew is corrected to shift the media perpendicular to the media feed direction. The method begins at 802 wherein the first roller is rotated faster than the second roller for inducing a skew to advance media along a media feed axis. At 804, the media 1 16 is reversed through a duplex path even as the angle the media 1 16 makes with the media feed direction is maintained. The skew is measured using sensors such as sensors 122, 124 at 806. At 808, the skew is removed via producing the speed differentials in the rollers as detailed herein.

[0029] Although described specifically throughout the entirety of the instant disclosure, representative examples of the present disclosure have utility over a wide range of applications, and the above discussion is not intended and should not be construed to be limiting, but is offered as an illustrative discussion of aspects of the disclosure.

[0030] What has been described and illustrated herein are examples of the disclosure along with some variations. The terms, descriptions and figures used herein are set forth by way of illustration and are not meant as limitations. Many variations are possible within the scope of the disclosure, which is intended to be defined by the following claims, and their equivalents, in which all terms are meant in their broadest reasonable sense unless otherwise indicated.